Elastic interactions of Fe adatoms on Cu(111) at the mesoscale

TL;DR

This paper applies an extended elastic eigenvector approach to model Fe adatom interactions on Cu(111), capturing oscillations, multisite effects, and anisotropies, with implications for adatom formation and diffusion.

Contribution

It introduces a sharp cutoff and considers interacting dimers in the elastic model, fitting three parameters to first-principles data for Fe on Cu(111).

Findings

Elastic interactions fit well at mesoscale separations.

Multisite and anisotropic effects are significant.

Model limitations at small separations are acknowledged.

Abstract

An extended elastic eigenvector approach had earlier been developed to interpret ab-initio calculations of adatom interactions. It shows oscillating interactions as well as trio- and quarto (multisite) terms within clusters. It is now applied to the interaction of Fe adatoms on Cu(111). The extended approach differs from previous calculations by using a sharp cutoff - generating oscillating interactions - and by taking into account interacting dimers - generating strong anisotropies and multisite terms. Additional weak anisotropy stems from the substrate and from the surface Brillouin zone shape. This approach has 3 free parameters which have been fitted to first principles interactions of Fe adatoms on Cu(111). Elastic adatom pair interactions and dimer-dimer interactions at mesoscale separations show a reasonable good fit to the first principles interactions. At smaller separations elastic interaction values remain questionable. To enable a comparison with future first principle calculations also dimer-monomer interactions are shown. Some conclusions on initial adatom formation and diffusion are proposed and open questions are formulated.